I think a better solution is to cap the whole top so water doesn't get in at all. I found that a plastic, clear SOLO container from my grocery store measures 1 3/4" deep by 4 5/8" diameter (I think it was on the olive bar for takeout). You can wiggle this in and place it over the everything so water does not get in at all. I will play with this because you need a way to secure it so it does not flop around - maybe silicon adhesive?

I plan to dry it out, paint the bolt with Rustoleum, then secure the cap over it.

I've been meaning to check this on my Leafs but forget when I actually have the hood opened. Well seeing this thread brought it to my attention again so I went out and checked my Leafs. Both my '12SL Japan built Leaf and '13S TN built didn't have any caps over the nut. All 4 nuts were quite rusted/corroded with the drivers side being worse shape than passenger side. My '13 currently had water sitting around the bolt, maybe 1/4" deep.My guess is the caps were just on the '11s and I agree a good glob of thick wheel bearing grease in the whole cup should help, after things have dried out. Poor design for sure.

On my 2013 SV, I found that the strut was only accessible after removing an access panel on the plastic trim piece. Also, there is no cap on my struts, so it would seem that those were only on 2011/2012 models.

A clear "Oikos" yogurt cup turned upside down also fits well over the bolt surround and sheds water. The cup is pretty sturdy, but a tight squeeze through the opening after snapping out the removable plastic grate section. A string used as a leash and a couple drops of silicone caulk should keep it from going astray over time. Then replace the grate.

Just did some research on this by referencing the FSU section of the service manuals from 2011 - 2015. The strut cap in question is present in the 2011 & 2012 service manuals, but has been deleted from the parts diagram from 2013 moving forward, although the 2013 and 2014 versions of the manual address re-installing the cap after re-assembly of the strut, so it's pretty clear they deleted the part, maybe for weight savings as this was one of the features they touted or the Gen 2 LEAF.

After seeing these posts, I got brave and called 1800NISSAN1. The Leaf customer service guy first told me that the strut tower cap USED to be carried by Nissan, but is not any more... When I gave him the part # 54330-ed000, he tried to get rid of my by making this deal with me::"I WILL AUTHORIZED A 0NE-TIME COURTESY TO PAY FOR THE PARTS... BUT... IF IN THE FUTURE, YOU NEED A NEW AIR CONDITIONER COMPRESSOR, THEN YOU WON'T GET IT BECAUSE YOU GOT YOUR "ONE-TIME COURTESY""

Isn't that a form of strong arm customer service? Anyway, I insisted that I wanted someone to determine that the tower caps SHOULD HAVE BEEN INCLUDED on the car when I bought it new. THE service guy promised to find out and get back to me... I know that these are $12 parts, but please Nissan, don't try to get rid of me...